Electron discharge device employing hollow resonator



May 16, 1950 L. F. BROADWAY ET AL 2,508,141

ELECTRON (DISCHARGE DEVICE EMPLOYING HOLLOW RESONATOR Filed July 26, 1945 M fir/ 2; I 20' 1/ MIC? j 24 I if INVENTORS' L EON/7R0 FRfl/VC/S BIPORDWHY HLBERT Ho/m'cE HTHER-roN ATTORNEY Patented May 16, 1950 UNITED STATES PATENT OFFICE ELECTRON DISCHARGE DEVICE EMPLOYING HOLLOW RESONATOR Application July 26, 1945, Serial No. 607,210 In Great Britain May 20, 1944 Section 1, Public Law 690, August 8, 1946 Patent expires May 20, 1964 15 Claims.

This invention relates to electron discharge devices employing cavity resonators.

A known form of electron discharge device of this kind comprises a cavity resonator through which a beam of electrons is projected so as to become velocity-modulated, the velocity-modulated beam then being directed towards a reflect ing electrode which serves to reflect the electrons back through the hollow resonator, the electron beam during its passage towards and away from the reflecting electrode becoming charge-density-modulated and imparting its energy to the resonator during its return therethrough so that the device functions as a generator of self-maintained oscillations. In such devices it is usually necessary to provide some adjustment of the resonator for tuning purposes and usually the resonator is provided with a flexible wall connected to adjusting mechanism whereby the flexible wall can be adjusted relatively to a fixed wall of the resonator whereby the resonant frequency of the resonator can be changed. In one form of such device the reflecting electrode structure is supported on the flexible wall of the resonator and adjustment of the flexible wall for tuning purposes is effected by coupling the reflecting electrode structure to a mechanism arranged externally of the device. In other devices a target or other electrode may be provided which is similarly mounted so that tuning of the resonator can be effected by coupling said target or other electrode structure to said mechanism. In such arrangements the resonator is supported in position in the device by a plurality of support rods extending from the pinch of the envelope of the device and it is found in practice that such a construction gives rise to difliculties owing to fortuitous changes in tuning which occur due to the expansion of the parts of the device when the latter is in operation. It will be appreciated from the construction described that when the reflecting electrode structure becomes heated due to the conduction of heat from the resonator, the reflecting electrode structure being rigidly supported at one end of the device moves in one direction whilst the support rods which also become heated by conduction and being rigidly supported at the opposite end of the device move on expansion in a direction opposite to the movement of the reflecting electrode structure. This consequently results in the two walls of the resonator being moved closer together when the device becomes heated thus causing an undesirable change in the resonant frequency of the resonator.

One of the objects of the present invention is to provide an improved electron discharge de' vice with a view to overcoming this difficulty.

According therefore to one feature of the present invention an electron discharge device is provided comprising a cavity resonator having a flexible wall and in which tuning is effected by deflecting said wall through the intermediary of a reflecting electrode or other structure mounted on said wall and wherein the resonator is supported in the envelope of the device by supporting means which is so attached tothe device that when the latter becomes heated during operation, expansion of the reflecting electrode structure and the supporting means cause movement of the flexible wall of the resonator and the other wall of the resonator in the same direction. By such an arrangement it is possible to maintain the resonant frequency of the resonator substantially constant during operation of the device or at least to reduce the change of the resonant frequency compared with the prior construction aforementioned. The compensation may be further improved by making the supports of different materials, e. g., nickel or Invar or other alloy so as to allow for differences in temperature which may develop during operation.

A further object of the invention is to provide an improved mechanism for mechanically adjusting the flexible wall of the resonator.

For the purpose of describing the invention more in detail reference will now be made to the accompanying drawing which illustrates partly in longitudinal section an electron discharge. device embodying the features of the present in vention.

As shown in the drawing, the reference numeral I indicates a rigid glass envelope wall, the lower end of which is completed by a. ring pinch, not shown, through which the leads to the various electrodes of the device are sealed, whilst the upper end of the envelope wall is closed by a metal disc 2 which is sealed to the upper end of the glass envelope I. The centre portion of the disc 2 is provided with circular corrugations 3 so as to enable the centre portion of the disc 2 to move axially with respect to the rigid envelope wall i. The disc 2 with its corrugations 3 thus forms a flexible wall for the envelope. The cavity resonator comprises a rigid wall 4 and a flexible wall 5 the latter being provided with circular corrugations, as shown, whereby the wall 5 can be moved towards or away from the wall 4 to adjust the resonant frequency of 3 the resonator. The wall 4 is provided with inner grid 6 and the wall with a grid 'i, the grid 5 being mounted on the inner end of a re-entrant portion of the wall 3, as shown, whilst an outer grid 8 is provided as indicated, this latter grid serving to ensure proper acceleration of electrons which emanate from a cathode ray gun indicated generally at 9. The cathode ray gun S is carried by a mica disc l9 which, in turn, is supported by a plurality of metal support rods it one of which is shown in the drawing. Preferably, three such rods are provided arranged equidistantly about the axis of the device. The resonator is also supported by the support rods H, the mica disc l6 and the resonator being secured to the rods H by the provision of sleeves I2 which are welded to the rods H and are flanged to embrace the mica disc la,"- and the resonator respectively in known manner. The upper ends of the support rods H are attached to the disc 2 whilst the lower ends of the rods II are supported from the ring pinch of the envelope by relatively flexible connections iii.

The reflecting electrode which is indicated by the reference numeral i i is secured at its upper end to a mica disc [5 which in turn is connected to a sleeve IS the lower end of which is attached to the flexible wall 5. The mica disc [5 is attached to a rod I! secured to the centre portion of the disc 2 and it will be appreciated therefore that if the centre portion of the disc 2 is moved axially with respect to the rigid wall i, the envelope, the flexible wall 5 of the resonator will be moved likewise axially whereby tuning of the resonator can be efiected. It will be appreciated that with the construction described, when the parts of the device become heated during operation and expansion occurs, expansion of the reflecting electrode structure will cause the flexible wall 5 of the resonator to move downwardly, and since the support rods H are attached to the disc 3 at their upper ends and are therefore rigidly maintained in position at these ends, expansion of the rods H when they become heated will cause the wall 3 of the resonator to move downwardly, so that movement of the walls 4 and 5 on expansion of the parts will occur in the same direction and the frequency of the resonator will remain substantially unchanged. It will of course be understood that the expansion of the support rods H will be accommodated by the relatively flexible supports [3. If required the various parts of the device can be made of different materials having such coefficients of expansion as to accommodate differences in temperature of the various parts which are likely to arise in operation so that despite such differences the tuning of the resonator can be maintained substantially constant.

In order to adjust the resonant frequency of the resonator, the outer surface of the centre portion of the disc 2 is attached to a rod l8 which is screw-threaded into a sleeve I9 which, in turn, is threaded into a supporting disc mounted in a metal cup or sleeve 24 which is attached to the disc 2. The supporting disc 25 is angularly movable in the cup 2| and is provided with screws 22, one of which is shown in the drawing, these screws passing through inclined slots 23, provided in the vertical Wall of the cup 2 l. Preferably, three inclined slots are provided and the supporting disc 20 is provided with three screws 22, the screws and slots being equidistantly arranged between the axis of the device. When these screws 22 are slackenecl the disc 20 can be rotated and due to the provision of the inclined slots which engage the screws 22 the disc 20 is caused to move axially on rotation, such axial movement being communicated to the flexible wall 5 of the resonator whereby a coarse adjustment of the resonant frequency can be obtained. When the screws 22 are tightened the disc 20 is held securely in position. The screw threads provided between the rod l8 and the sleeve l9 and between the sleeve l9 and the supporting disc 20 are so chosen that when the sleeve :3 is rotated a differential movement is imparted to the rod 18, this movement also being communicated to the flexible wall 5 and serving to effect a fine adjustment of the resonant frequency.

Usually, in devices of the form described. the lead to the reflecting electrode is taken through the end of the envelope remote from the end through which the leads to the other electrodes are taken. In the present arrangement the lead for the reflecting electrode indicated at 24 is taken to the lower end of the envelope through which the rest of the leads pass thus leaving the upper end of the envelope free for the connection of the tuning mechanism and avoiding the necessity of an insulated seal through the metal disc 2. The envelope I is surrounded by a metal screen 25 which serves to screen all of the leads to the various electrodes, the screen 25 being secured at its upper end to the cup 2| and at its lower end to the base 26 of the device, the base 26 being preferably of the so-called Octal type. The output from the resonator is taken therefrom through a concentric line 21 the inner conductor of which terminates in a coupling loop 28 projecting into the resonator, whilst outer conductor is connected to the resonator, the concentric line 2! also being sealed to the ring pinch at the base of the device.

In order to permit the required movement of the resonator when the parts become heated the concentric line 2'! should be sufliciently flexible.

What we claim is:

1. An electron discharge device including a resonator having a rigid and a flexible wall, a rigid supporting structure for said resonator, elongated rigid supporting means connected between said supporting structure and said rigid resonator wall and other elongated rigid supporting means connected between said supporting structure and. said flexible resonator wall and including an electrode rigidly connected to said flexible wall, said rigid supportin means extend ing in the same direction from said resonator walls, so that they will expand in the same direction when subjected to heat, whereby the spacing of said walls of said resonator remains substantially constant.

2. An electron discharge device includin a cavity resonator having a rigid and a flexible wall for tuning, a supporting structure for said resonator having elongated rigid supporting elements connected to said rigid resonator wall and having a flexible portion, an electrode rigidly connected to said flexible wall and elongated rigid means connected between said electrode and said flexible portion, and means adjustably connecting said flexible portion and said structure for tuning said resonator, said rigid supporting elements and said rigid means extending in the same direction from said resonator walls, so that they will expand in the same direction when subjected to heat, whereby the spacing of the Walls of said resonator remains substantially constant.

3. An electron discharge device including acavity resonator having a rigid and a flexible wall for tuning an envelope containing said resonator and having rigid supporting elements connected to, said rigid resonator wall and having a flexible portion, an electrode rigidly connected to said flexible wall, rigid means connected between said electrode and said flexible portion, said rigid supporting elements and means for tuning said resonator comprising a differential screw mounted on the outside of said envelope and secured to said flexible portion.

4. An electron discharge device including a cavity resonator having a rigid and a flexible wall for tuning, a supporting structure for said resonator including a plurality of elongated support rods rigidly attached at one end to said supporting structure and extending toward and secured to said resonator, the free ends of said rods being free to move on expansion of said rods, a reflecting electrode rigidly connected to said flexible wall and elongated rigid means connected between said reflecting electrode and said supporting structure, said support rods and rigid means extending in the same direction from said resonator walls, so that they will expand in the same direction when subjected to heat whereby the spacing of the walls of said resonator remains substantially constant, said elongated rigid means including means for moving said reflecting electrode to move said flexible wall including an angularly movable member mounted on said supporting structure and having inclined surfaces contacting said supporting struture for moving said member axially upon rotation of said member and means connecting said angularly movable member with said electrode.

5. An electron discharge device having an envelope provided with a flexible wall, a cavity resonator mounted within said envelope and having a flexible wall, rigid supporting rods supporting said resonator within said envelope, said rods being connected to the wall of said envelope and to said resonator, a, reflecting electrode rigid- 1y connected to the flexible wall of said resonator, a rigid connection between said reflecting electrode and the flexible wall of said envelope, means supported on the exterior of said envelope and including a cup member having inwardly projecting elements extending radially into said cup member, a ring member having inclined slots in the periphery thereof, said slots receiving said inwardly projecting elements, and connections between said ring member and the flexible wall of said envelope whereby upon angular rotation of said ring member said connections will be moved axially to flex the flexible walls of said envelope and said resonator for tuning said resonator.

6. An electron discharge device having an envelope provided with a flexible wall, a cavity resonator mounted within said envelope and having a flexible wall, rigid supporting rods supporting said resonator within said envelope, said rods being connected to the wall of said envelope and to said resonator, a reflecting electrode rigid- 1y connected to the flexible wall of said resonator, a rigid connection between said reflecting electrode and flexible wall of said envelope, means supported on the exterior of said envelope and including a cup member having inwardly projecting elements extending radially into said cup member, a ring member having inclined slots in the periphery thereof, said slots receiving said inwardly projecting elements, and connections between said ring member and the flexible wall of said envelope whereby upon angular rotationof said ring member said connections will bemoved axially to flex the flexible walls of said envelope and said resonator for tuning said resonator, said rods, said reflecting electrode and its supporting element having a coefficient of expansion such that they expand equally in the same direction when subjected to heat to main-- tain the spacing of the walls of said resonator substantially constant.

7. An electron discharge device having an elon-- gated envelope and provided at one end thereof with a flexible wall, a cavity resonator mounted within said envelope and having a rigid and a flexible wall, a reflecting electrode ri idly connected to the flexible wall of said resonator, rigid rod connections mounted at one end on the wall of said envelope and supporting said resonator, a rigid connection between said reflecting electrode and the flexible wall of said envelope, said rods and said reflecting electrode and its rigid connection having equal coefiicients of expansion, whereby when subjected to heat elongation will occur in the same direction whereby the spacing between the walls of said resonator is maintained substantially constant, a cup shaped element mounted on the end of said envelope adjacent said flexible wall, a differential screw structure mounted in said cup-shaped member and having relative rotation therewith and connected to the flexible wall of said envelope for moving said flexible wall axially for'flexing the flexible walls of said envelope and said resonatorfor tuning said resonator. I

8. An electron discharge device having an elongated envelope and provided at one end thereof with a flexible wall, a cavity resonator mounted within said envelope and having a flexible wall, a reflecting electrode rigidly connected to the flexible wall of said resonator, rigid rod connections mounted at one end on the wall of said envelope and supporting said resonator, a rigid connection between said reflecting electrode and the flexible wall of said envelope, a cup shaped element mounted on the end of said envelope adjacent the flexible wall, a differential screw structure mounted in said cup-shaped member and having relative rotation and connections between the flexible wall of said envelope and said screw structure for flexing the walls of said envelope and said resonator for tuning said resonator.

9. An electron discharge device comprising a cavity resonator having a rigid wall and a flexible wall, and a supporting structure for said resonator including a rigid support member, elongated first supporting means rigidly connected between said member and said rigid resonator Wall, and elongated second supporting means parallel to said first supporting means and rigidly connected to said flexible resonator wall and to said member adjacent the connection thereof to said first supporting means and independently of said first supporting means, whereby said first and second supporting means expand in the same direction relative to said support member when subjected to heat, to maintain the spacing between the flexible and rigid walls of said resonator substantially constant.

10. An electron discharge device including an envelope, a cavity resonator mounted within said envelope and having a rigid wall and a flexible wall, a plurality of support rods rigidly connected between a portion of said envelope and said rigid resonator wall, and elongated means rigidly conmeeting said flexible resonator wall and said portion of said envelope independently of saidrods, whereby saidrods and said elongated means expand in the same direction relative to said envelope when subjected to heat, to maintain the spacing between the flexible and rigid walls of said resonator substantially constant.

11. An electron discharge device including an envelope, a cavity resonator mounted within said envelope and having a rigid and a flexible wall, a plurality of support rods rigidly connected between a portion of said envelope and said rigid resonator wall, a reflecting electrode within said envelope spaced from and rigidly connected to said flexible resonator wall, and elongated means rigidly connected between said electrode and said portion of said envelope independently of said rods, whereby said rods, electrode and elongated means expand in the same direction relative to said envelope when subjected to heat, to maintain the spacing between the flexible and rigid walls of said resonator substantially constant.

'12. An electron discharge device according to claim 9, wherein said second supporting means includes a pair of relatively adjustable elements and means for changing the adjustment of said elements for tuning said resonator.

13. An electron discharge device according to claim 12, wherein said rigid support member is an envelope containing said resonator and said first supporting means and having a flexible wall forming a portion of said second supporting means, said adjustable elements and said adjustment changing means being located outside said envelope.

14. An electron discharge device comprising an envelope having a rigid and a flexible wall, a cavity resonator mounted within said envelope and having a rigid and a flexible wall, supporting means rigidly connected between said rigid envelope wall [and said rigid resonator wall, a first rigid connection between said flexible resonator wall and said flexible envelope wall, a second rigid connection outside said envelope between said flexible envelope wall and said rigid envelope wall, and means for adjusting the length of said second rigid connection for tuning said resonator.

15. An electron discharge device of the electron velocity modulation type comprising an envelope having a. rigid and a flexible wall and containing a cathode, a cavity resonator and a reflector electrode, means rigidly connecting said reflector electrode and said flexible envelope wall, said cavity resonator having an apertured rigid wall and an opposed apertured flexible wall disposed between and in alignment with said cathode and said reflector electrode, means rigidly connecting said flexible resonator wall and said reflector electrode, supporting means rigidly connected between said rigid resonator and envelope walls, adjustable means otuside said envelope rigidly connected between said rigid and flexible envelope walls, and means for adjusting the length of the last-named means, whereby the spacing of said reflector electrode and said flexible resonator wall relative to said rigid resonator wall may be adjusted for tuning said resonator.

LEONARD FRAN CIS BROADWAY. ALBERT HORACE ATI-IERTON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,380,496 Beard July 31, 1945 2,394,396 Mouromtseif et al. Feb. 5, 1946 2,408,817 Snow Oct. 8, 1946 2,411,912 Vance Dec. 3, 1946 2,454,306 Clifford et al Nov. 23, 1948 Disclaimer 2,508,141.Le0nard Fmncz's Bwoadway, Ickenham, and Albert H omce lithe?- ton, Hayes, England. ELECTRON DISCHARGE DEVICE EMPLOYING HOL- LOW RESONATOR. Patent dated May 16, 1950. Disclaimer filed Feb. 1, 1951, by the assignee, Electric c6 Musical Industries Limited. Hereby enters this disclaimer to claims 3 and 14 of said patent.

[Oficz'al Gazette March 13, 1.951.] 

